Furnace access apparatus



Sept 21, 1955 E. c. MILLER 3,207,132

FURNACE ACCESS APPARATUS Filed Jan. 27, 1964 2 Sheets-Sheet l Je. .sz sa. ,n

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faQ/w TTORNE Y Sept 21, 1965 E. c. MILLER 3,207,132

FURNACE ACCESS APPARATUS Filed Jan. 27. 1964 2 Sheets-Sheet 2 EARLE C. MILLER INVENTOR.

United States Patent O 3,207,132 FURNACE ACCESS APPARATUS Earle C. Miller, Worcester, Mass., assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Filed Jan. 27, 1964, Ser. No. 340,372 4 Claims. (Cl. 122-235) This invention relates to a furnace access apparatus and, more particularly, to apparatus arranged to permit observation of the interior of a furnace or the introduction of tools therein.

It is necessary, on occasion, in the steam generating field not only to be able to observe the interior of the furnace but also at times to permit the introduction of lancing tools, soot blowers, or the like into the furnace. In some cases, it is necessary to be able to permit a man to enter the furnace. Such access doors present a number of problems not the least of which (particularly in the case of a pressurized furnace) is the release of dangerous and dirt-laden gases into the area surrounding the steam generating unit. If the steam generating unit is enclosed in a building, of course, the gases can be a constant danger to the operating personnel. So far as dust is concerned, this is not only a housekeeping problem, so far as the maintenance of machinery and the comfort of` the operating personnel is concerned, but, in the case of an outdoor installation, the dust can be a nuisance. Furthermore, the leakage of gases outwardly of the furnace can affect its efliciency. Attempts to solve these problems have resulted in very expensive access doors with substantial maintenance problems. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a furnace access apparatus which may be used with pressurized furnaces or the like and which will not permit the leakage of combustion gases outside of the furnace.

Another object of this invention is the provision of a furnace access apparatus which is inexpensive to manufacture, which is not diflcult to maintain, and which, at the same time, presents no leakage problem.

A further object of the present invention is the provision of a furnace access apparatus making substantial use of conventional elements already present in the furnace with a resultant saving in cost.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to one of its structural forms as illustrated by the accompanying drawings in which:

FIG. l is a vertical sectional view of a steam generating unit incorporating a furnace access apparatus constructed in accordance with the principles of the present invention;

FIG. 2 is a horizontal sectional view of the steam generating unit taken on the line II-II of FIG. l; and

FIG. 3 is a vertical sectional view of the apparatus taken on the line III-III of FIG. 2.

Referring rst to FIG. l, wherein are best shown the general features of the invention, the furnace access apparatus, indicated generally by the reference numeral 10, is shown in use with a steam generating unit 11 having a furnace 12 and a boiler 13 mounted on a structural framework 14. The furnace consists of a front wall 15, a rear wall 16, and side walls 17 defining a combustion chamber 18. Underlying the combustion chamber is a furnace bottom 19.

ICC

The furnace walls are lined with water-wall tubes and the tubes in the front wall 15 are bent inwardly to form an abutment 21 having mounted on its downwardlydirected surface a series of burners 22. Similarly, the tubes in the rear wall 16 are bent inwardly to form an abutment 23 on whose downwardly-directed surface is mounted a series of burners 24.

The boiler 13 is provided with a steam-and-water drum 25 containing steam-purifying elements and from which extend downcomer tubes 26 leading to a lower drum 27. Large downcomer pipes 28 lead from the lower drum 27 to a horizontal header 29 extending around the bottom of the furnace and from which water-wall tubes 31 extend along tbe walls of the furnace. The tubes extending along the surface of the rear wall 16 are bent forwardly in the upper part of the furnace to form a nose 32 which underlines a furnace exit and which nose denes with the front wall 15 a narrow passage 33 overlying the combustion chamber 18. The nose forms with the roof 35 of the furnace a furnace exit passage 34. A baffle 36 extends downwardly from the steam-and-water drum 25 and serves to define a back pass 37 and a back pass 38, the downcomer tubes 26 residing in the back pass 38 which, in turn, is connected to a breaching 39 provided with a dust collector 41.

A duct 46 extends from the forced draft fan and air heater (not shown) to the furnace and is provided with vertically-extending branch ducts 47 and 48 which extend downwardly toward the burners 22 and 24. The branch duct 47 extends downwardly and is connected to the center of a horizontal air duct 42, while the branch duct 48 is connected to a horizontal air duct 43.

Referring now to FIG. 2, it can be seen that the horizontal duct 43 is fastened to the front wall 15 in an airtight manner and that the branch duct 48 extends from its center portion. The apparatus is shown as provided with two burners 22 of the directional-flame type each spaced a third of the distance across the furnace from its corresponding side wall 17. Mounted on the front wall 15 between one of the burners 22 and the side wall 17 is an inner door 44, while an outer door 45 is mounted on the outer wall of the duct 43. The center of the door 44 and the cent-er of the door 45 lie on a line extending perpendicular to the surface of the wall 15 at that point. As is evident in the drawing, the water-wall tubes 31 of the front wall 15 are bent rearwardly and laterally to provide an opening 49 in which the inner door 44 is mounted. A similar inner door 51 is mounted between the two burners 22, while another inner door 52 is mounted between the other side wall 17 and its adjacent burner 22. The inner door 51 is provided with a corresponding outer door 53, while the inner door 52 is similarly provided with an outer door 54.

Turning now to FIG. 3, it can be seen that the duct 43 is formed with three walls including an outer wall 55, an upper wall 56, and a lower wall 57, all formed of sheet metal. The inner edge of the upper wall 56 and the inner edge of the lower wall 57 are both firmly attached as by welding to the water-wall tubes forming the front wall 15 of the furnace. The outer door 45 is, of course, mounted on the outer wall 55 and consists of a door 58 having a handle 59, the door being hingedly mounted on a frame 61 which is fastened around an opening in the wall 55. A seal 62 extends between the frame 61 and the door 58. The inner door 44 is shown as consisting of a frame 63 of recessed cross-section having a rearwardly-directed flange 64 into which is slid a block 65 of solid refractory having a handle 66 mounted in its center. The body of plastic refractory 67 lls the space inside of the duct 43 behind the tubes 31 and the opening 49 and around the frame 63 of the door. This refractory is formed in a tapered manner to form a conical recess 68 extending rearwardly from the door 44.

The operation of the apparatus will now be readily understood in view of the above description. The steam generating unit 11 operates in the usual manner. Preheated air arrives through the duct 46 and passes through the branch ducts 47 and 48 to the cross ducts 42 and 43, respectively. Air leaves the cross ducts and passes through the burners 24 and 22, is mixed with the fuel, and then enters the combustion chamber for ignition and combustion. The hot products of combustion pass upwardly through the combustion chamber 18, while certain unburnable elements of the fuel pass downwardly and fall on the furnace bottom 19. Hot gases pass upwardly around the nose 32 through the passage 33 and then into the back passes through the furnace exit passage 34. They pass downwardly through the back pass 37 and then upwardly through the back pass 38 flowing over the downcomers 26. Eventually, the gases pass into the breaching 39 where dust is removed by the dust collector 41. The gases then pass through the air heater and up the stack. As is evident in FIG. 3, the furnace access apparatus is provided with Irelatively inexpensive inner door 44 and outer door 45. These doors under normal pressurized furnace operation would leak gas and dust rather badly. In the present situation, however, these doors are intended to be used only when the furnace is shut down. They would not be open while the burners are operating. However, while the burners are operating, an access door does tend to leak. However, in the case of the present invention, the air passing downwardly from the branch duct 48 lille the cross duct 43 with air at a pressure which is slightly greater than the pressure on the interior of the furnace. This air in the duct, of course, passes through the burners 22 and takes part in the combustion process. The air in the duct leaks around the door 44, since it is a simple, inexpensively-constructed door having only the refractory block 65 tting loosely within the flange 64 of the frame 63. However, this leakage takes place inwardly of the furnace, so that the air that leaks in this manner takes part in the combustion process. Under normal circumstances, the outer door 4S will also leak slightly, despite the presence of the seal 62 between the door 58 and the frame 61. However, what leaks around this door is air and, even though it is preheated air, its loss presents no problem. In any case, such pre-heated air is not poisonous and it does not carry dust in it, so that no harm is done.

It can be seen, then, by use of the present invention it is possible to provide access doors which are particuarly useful with the so-called pressurized furnace. The invention takes advantage of the fact that the inventor has recognized that access doors are prone to leakage and has used this leakage to his own advantage. By permitting air from the duct or housing surrounding the inner door t0 leak into the furnace and also to leak slightly from the outer door, he is assured that in any case poisonous dusty combustion gases do not leak out of the furnace. No matter how well made an access door may be, the shifting of the furnace and the expanding and contraction during use of the furnace is going to eventually cause cracks and mists which will leak and the present invention assures that the leakage that does take place is neither dangerous nor a detriment to good housekeeping around the steam generating unit.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent, is:

l. A furnace access apparatus, comprising (a) a furnace wall having an opening therethrough, the furnace wall being made up of water bearing tubes and wherein the said opening is formed by bending a number of these tubes rearwardly and laterally,

(b) an inner door mounted in the opening and normally closing it,

(c) a housing defining a chamber mounted on the outer surface of the wall and enclosing the opening, the housing extending continuously horizontally across the furnace wall,

(d) a burner mounted on the wall within the housing and receiving combustion air from within the housma,

(e) means maintaining the air pressure in the housing greater than the pressure in the furnace, and

(f) a normally-closed outer door associated with the housing and located in alignment with the said inner door, the chamber being unobstructed in the vicinity of the said doors.

2. A furnace access door as recited in claim 1, wherein the inner door consists of a frame fastened in the opening and a block of refractory material held in the frame so as to be readily removable.

3. A furnace access apparatus as recited in claim 1, wherein the furnace wall is provided with an abutment extending horizontally across the furnace, the abutment having an upwardlly-directed portion and a downwardlydirected portion, the said opening being located on the downwardly-directed portion and wherein the burner is also mounted on the downwardly-directed portion, the burner receiving air from within the housing.

4. A furnace access apparatus as recited in claim 1, wherein the centers of the inner and outer doors lie on a line perpendicular to the plane of the furnace in the vicinity of the opening.

References Cited by the Examiner UNITED STATES PATENTS 2,229,068 1/41 Frisch 122-235 2,524,795 10/ 50 Hermandorfer 126-200 2,947,289 8/ 60 Miller 122-479 FOREIGN PATENTS 151,638 5/53 Australia. 8,169 l0/5 l Great Britain.

PERCY L. PATRICK, Primary Examiner.

KENNETH W. SPRAGUE, Examiner. 

1. A FURNACE ACCESS APPARATUS, COMPRISING (A) A FURNACE WALL HAVING AN OPENING THERETHROUGH, THE FURNACE WALL BEING MADE UP OF WATER BEARING TUBES AND WHEREIN THE SAID OPENING IS FORMED BY BENDING A NUMBER OF THESE TUBES REARWEARDLY AND LATERALLY, (B) AN INNER DOOR MOUNTED IN THE OPENING AND NORMALLY CLOSING IT, (C) A HOUSING DEFINING A CHAMBER MOUNTED ON THE OUTE SURFACE OF THE WALL AND ENCLOSING THE OPENING, THE HOUSING EXTENDING CONTINUOUSLY HORIZONTALLKY ACROSS THE FURNACE WALL, (D) A BURNER MOUNTED ON THE WALL WITHIN THE HOUSING AND RECEVING COMBUSTION AIR FROM WITHIN THE HOUSING, (E) MEANS MAINTAINING THE AIR PRESSURE IN THE HOUSING GREATER THAN THE PRESSURE IN THE FURNACE, AND (F) A NORMALLY-CLOSED OUTER DOOR ASSOCIATED WITH THE HOUSING AND LOCATED IN ALIGNMENT WITH THE SAID INNER DOOR, THE CHAMBER BEING UNOBSTRUCTED IN THE VICINITY OF THE SAID DOORS. 